Example for radar #4992296676229120.
=== TITLE ===
NSCollectionView wrongly allows multiple selection
=== Explanation ===
NSCollectionView allows multiple selection when an item is already selected and a user holds down the shift key and presses an arrow key.
Doesn't happen when using the mouse to click on collection view items.
=== REPRO ===
Create an NSCollectionView. collectionView.selectable = true collectionView.allowsEmptySelection = true collectionView.allowsMultipleSelection = false
Click to select a cell. Select any item by clicking on it. Hold down shift and press the right arrow key. Multiple items are selected
=== Expected Behavior ===
Previously selected item is deselected and new item is selected Only one item is selected
=== Observed Behavior ===
Previously selected item is still selected and a new item is also selected Multiple items are selected
=== Environment ===
Xcode 7.2.1 (7C1002) OS X 10.11.3 (15D21)